1. Field of Disclosure
The present disclosure relates to a terminal device technology, more particularly, to a charging system for a terminal, a charging method for the terminal, and a power adapter.
2. Description of Related Art
Currently, mobile terminals (such as a smart phone) are increasingly popular with consumers. However, the mobile terminals consume a great amount of power so that they need to be charged frequently.
The mobile terminals are usually charged through power adapters. A power adapter generally includes a primary rectifier circuit, a primary filter circuit, a transformer, a secondary rectifier circuit, a secondary filter circuit, and a control circuit, etc. The power adapter converts input 220V alternating current (AC) power into a stable low-voltage direct current (DC) power (such as 5V) suitable for the mobile terminal, so as to provide power to a power management device and a battery of the mobile terminal, thus charging the mobile terminal.
However, as the power of the power adapters increases, for example, when the power is upgraded from 5 W to a higher power, such as 10 W, 15 W, 25 W etc., more electronic components that can sustain a higher power and realize a higher control of accuracy are needed for complementing each other. This causes size of the power adapters to increase as well as manufacturing difficulty of the adapters to also increase.
In general, current flowing through the power adapter of related art is detected with a current sensing resistor and an operational amplifier. The sensing current becomes greater as power of the power adapter becomes greater. Correspondingly, under the premise that the operational amplifier is not saturated, the dynamic range of the detective current is more limited. However, when the mobile terminal is charged with small current outputted by the power adapter, a wider dynamic range of the operational amplifier by using a smaller current sensing resistor or selecting a lower amplification of the operational amplifier) may result in inaccuracy of detection of the small current because of the characteristic of the operational amplifier, which further affects the application of the power adapter.